On Thu, 13 May 2010, Tony Lindgren wrote: > * Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> [100513 07:11]: > > On Wed, 12 May 2010, Paul Walmsley wrote: > > > > > Hello, > > > > > > Some general comments on the suspend blockers/wakelock/opportunistic > > > suspend v6 patch series, posted here: > > > > > > https://lists.linux-foundation.org/pipermail/linux-pm/2010-April/025146.html > > > > > > The comments below are somewhat telegraphic in the interests of > > > readability - more specific comments to follow in later E-mails. I am > > > indebted to those of us who discussed these issues at LPC last year and > > > ELC this year for several stimulating discussions. > > > > > > There are several general problems with the design of opportunistic > > > suspend and suspend-blocks. > > > > > > 1. The opportunistic suspend code bypasses existing Linux kernel code, > > > such as timers and the scheduler, that indicates when code > > > needs to run, and when the system is idle. > > > > Whoa! That's not my understanding at all. > > > > As I see it, opportunistic suspend doesn't bypass any code that isn't > > already bypassed by the existing suspend code. Users can do > > > > echo mem >/sys/power/state > > > > whenever they want, without regard to kernel timers and the scheduler > > (other than the fact that the user's thread must be running in order to > > carry out the write, of course). > > The difference between echo mem > /sys/power/state and suspend blocks > is that with suspend blocks the system keeps running. Irrelevant. Paul wasn't talking about the suspend blockers; he was talking about opportunistic suspend. So what's the difference between opportunistic suspend and "echo mem >/sys/power/state"? Especially when suspend blockers aren't being used? > And that's why > it should be handled by runtime power management instead. Runtime PM is not capable of freezing userspace and shutting down CPUs. More or less by definition -- if it could then it wouldn't be "runtime" any more, since the processor wouldn't be running. > The suspend blocks seems like a hack to spam filter good and bad > apps from timer usage point of view. Applications are categorized > as good or bad depending if they grab a susped blocker or not. You're referring just to the userspace part of the suspend blocker API. What about the kernel part? > I believe categorizing the apps should be instead done with some > timer flags or cgroups instead. That would be compatible with using suspend blockers. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
